1. Field of the Invention
The invention relates to an insulating plate, an insulating plate manufacturing method and a terminal block.
2. Description of the Related Art
Japanese Unexamined Patent Publication No. 2008-98007 discloses a terminal block for electrically connecting conductors, such as busbars, extending from electrical devices, such as a motor and an inverter. This terminal block electrically connects the conductors by placing the conductors of the respective electrical devices one above another on metal nuts insert molded in a terminal block main body and fastening the conductors by tightening bolts and the nuts.
The electrical devices generally generate high levels of heat and cause the conductors to become hot. Hence, a metal heat sink is arranged below the nuts via an insulating member in the form of a flat plate made of synthetic resin. Heat transferred from the conductors to the nuts is transferred to the heat sink via the insulating member and is radiated from the heat sink in the terminal block.
Attempts have been made to form the insulating member with recesses to accommodate the nuts. More particularly, a mold is provided with mold pins for forming the recesses. However, a resin molded article, such as the insulating member, generally contracts when being separated from the mold, and it is difficult to separate the resin molded article from the mold due to the mold pins fit in the recesses. Thus, the insulating member is separated from the mold by ejector pins that push the bottom surfaces of the recesses. However, the ejector pins leave slight indents on the bottom surfaces of the recesses. The indents caused by the ejector pins result in air layers between the lower surfaces of the nuts and the bottom surfaces of the recesses. These air layers have lower thermal conductivity than metals, synthetic resins and the like. As a result, heat is not transferred as efficiently from the nuts to the heat sink, thereby reducing heat radiation performance. This phenomenon also could occur on a boundary surface between the insulating member and the heat sink.
The present invention was completed in view of the above situation and an object thereof is to improve heat radiation performance of a terminal block.